Ethylene dichloride (1,2-dichloroethane) is typically produced by catalytic vapor phase oxychlorination of ethylene wherein a gaseous mixture of ethylene, hydrogen chloride, and oxygen are reacted in the presence of a Deacon-type catalyst, e.g., copper halide catalyst. The oxychlorination product gas stream is condensed to form organic and aqueous acidic liquid phases. The organic phase containing crude ethylene dichloride is further purified by, for example, distillation and the aqueous acidic phase is discharged to waste.
Although satisfactorily high yields of ethylene dichloride may be obtained by the vapor phase oxychlorination of ethylene, both the organic and aqueous phases typically contain objectionable amounts of chloral, i.e., from about 0.2 to 0.5 percent by weight, in the organic phase and in excess of 2 percent by weight in the aqueous phase.
Since chloral is classified as a pollutant, it must be substantially removed from the aqueous phase prior to discharge to waste and also must be removed from the organic phase in order to produce high purity ethylene dichloride.
One means of removing chloral from the condensed oxychlorination product stream is disclosed in U.S. Pat. No. 3,378,597 wherein aqueous sodium hydroxide is used to decompose chloral to chloroform and sodium formate. However, both chloroform and sodium formate also pose a waste disposal problem and require additional treatment, e.g., bioxidation or the like, before being discharged to a receiving stream.
It is desirable, therefore, to devise means for removing chloral prior to condensing the gaseous oxychlorination product stream which would preclude further treatment of both the organic and aqueous phases to remove chloral therefrom.